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"Dalam dunia penerbangan diperlukan adanya komunikasi antara petugas pengatur lalu lintas penerbangan dengan pilot pesawat melalui perangkat towerset yang bekerja dalam modulasi AM. Pada saat ini monitor operasional towerset adalah melalui kelengkapan lokal radio, sehingga jika terjadi kerusakan di jalur power ke antena tidak akan bisa terdeteksi dari ruang teknisi. Pada penelitian ini dibuat suatu sistem yang dinamakan towerset monitor yang selain menampilkan ketidak normalan perangkat di layar monitor juga dilengkapi dengan sistem peringatan melalui SMS sehingga bisa diakses langsung oleh teknisi. Akuisisi data dari sistem towerset menggunakan micro controller AVR 8535 dan modem GSM. Besaran yang dimonitor berupa SWR, reflected power, PTT command dan power forward. Aplikasi akan mengolah data dari microcontroller untuk ditampilkan di monitor serta dikirimkan melalui SMS ke personel yang telah ditentukan. Batasan keadaan tidak normal adalah jika SWR di atas 2, power forward kurang dari 70% dan power reflected lebih dari 30 % dari RF power maksimal. Sistem towerset monitor berhasil diimplementasikan dengan losses RF power pada directional coupler sebesar 1,305 Watt dimana losses tersebut masih berada pada batas toleransi.

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During the flight, communication between the air control officer and pilot through the towerset device that works in the modulation AM is required. At the moment operational monitoring of towerset was done by local radio equipment, so that if damage occurs in the path of power to the antenna will not be detected from the technicians room. This research created a system called towerset monitor which in addition to showing abnormalities on the monitor screen device also comes with a warning system via SMS thus can be accessed directly by a technician. Acquisition of data from systems using micro controller towerset AVR 8535 and GSM modems. The quantity to be monitored are in the form of SWR, reflected power, PTT command and power forward. The application will process the data from the microcontroller to be displayed on a monitor and sent via SMS to the authorized personnel. Boundary condition for the abnormality is if the SWR is above 2, power forward is less than 70% and reflected power is more than 30% of the maximum RF power. Tower system is successfully implemented with a set of monitors RF power losses in the directional coupler of 1.305 Watt. The losses are still at the limit of tolerance."

"ABSTRAKDivais directional coupler dan optical switch merupakan komponen yangdibutuhkan dalam pemrosesan sinyal optik. Kemajuan teknologi wavelength divisionmultiplexing (WDM) dan pertumbuhan lalu lintas internet yang cepat memicu banyakpenelitian tentang teknologi switching optik. Galium Nitrida (GaN) merupakan materialsemikonduktor nitrida kelompok III yang menjadi kandidat menjanjikan untuk divaisyang beroperasi pada panjang gelombang komunikasi optik.Pada penelitian ini dilakukan desain directional coupler dan optical switchmenggunakan material GaN untuk panjang gelombang telekomunikasi, yaitu 1,55 um.Desain directional coupler terdiri dari pandu gelombang S-bend dan linear sedangkandesain optical switch berbasis Mach-Zehnder Interferometer yang terdiri dari duadirectional coupler yang dihubungkan dengan dua lengan persegi panjang. Optimasidesain dilakukan dengan metode finite difference beam propagation method (FD-BPM)menggunakan perangkat lunak OptiBPM. Optimasi dilakukan dengan memvariasikanparameter pandu gelombang meliputi lebar, ketebalan, width gap dan coupling gap.Dari hasil simulasi ditunjukkan bahwa lebar dan tebal terbaik untuk memperolehpropagasi single mode masing-masing adalah 4 um. Selanjutnya, berdasarkan hasiloptimasi ukuran pandu gelombang dilakukan desain directional coupler dan opticalswitch. Ditunjukan bahwa directional coupler dengan panjang 980 um dan lebar 15 umdengan width gap 7 um dan coupling gap 6 μm menghasilkan daya keluaran sebesar91,71% dengan splitting ratio sebesar 48,83% : 48,03%, excess loss dan power imbalanceberturut-turut sebesar 0,37 dB dan 0,07 dB.Tahap selanjutnya, berdasarkan lebar dan tebal pandu gelombang, dilakukanoptimasi desain optical switch. Dari hasil eksperimen numerik ditunjukkan bahwa desainoptical switch terbaik, memiliki panjang 6380 μm dan lebar 15 um, dengan panjangelektroda sebesar 4500 μm. Optical switch mampu beroperasi sebagai switch pada
 =34 V dengan insertion loss dan extinction ratio berturut-turut sebesar 1,23 dB dan 8,46 dB

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ABSTRACTDirectional coupler and optical switches are the components needed in opticalsignal processing. The progress of wavelength division multiplexing (WDM) technologyand the rapid growth of internet traffic have triggered much research regarding opticalswitching technology. Gallium Nitride (GaN) is a III-nitride semiconductor becomes apromising candidate for devices which operate in wavelength optical communications.In this research, the design of GaN-based directional coupler and optical switchdesign was conducted for telecommunication wavelength at 1.55 um. The design ofdirectional coupler consists of S-bend and linear waveguide, whereas, design of opticalswitch based on Mach-Zehnder Interferometer consists of two directional couplersconnected by two rectangular arms. Design optimization was conducted by finitedifference beam propagation method (FD-BPM) using OptiBPM software. Optimizationwas conducted by a varying waveguide parameter such as waveguide width, waveguidethickness, width gap and coupling gap.From the simulation results, the best of width and thickness were 4 um and 4 um,respectively, for support single-mode propagation. Next, based on the optimization resultof the waveguide dimension, it was conducted a design of the directional coupler andoptical switch. It was noticed that the directional coupler was 980 m long, and 15 umwide with width gap and coupling gap were 7 um and 6 μm, respectively. It generatedthe output power of 91.71% with the splitting ratio of 48.83 %: 48.03% while the excessloss of 0.37 dB and the power imbalances of 0.07 dB.The next step, optimization of the optical switch design was conducted based onthe width and thickness of the waveguide. From the simulation result, the best design ofthe optical switch was 6380 μm long and 15 um wide, with the electrode length was 4500μm. The optical switch could operate as an optical switch at = 34V with an insertionloss of 1.23 dB and an extinction ratio of 8.46 dB."

"ABSTRAKKemajuan teknologi telah mendorong pengembangan material dasar semikonduktor. Beberapa dekade terakhir material Galium Nitrida telah menarik para peneliti untuk dikembangkan karena memiliki beberapa kelebihan, antara lain stabil terhadap suhu yang tinggi, memiliki tingkat penumbuhan epitaksi yang tinggi, konsumsi daya yang rendah dan memiliki celah pita langsung yang tinggi. Hingga saat ini, penelitian terkait pemanfaatan material GaN sebagai divais fotonik aktif telah banyak dilakukan, seperti LED, dioda laser dan detektor. Namun riset material GaN pada divais fotonik pasif, yakni divais berbasis pandu gelombang hingga kini masih sangat minim ditekuni oleh para peneliti. Termotivasi oleh hal tersebut, pada skripsi ini dilakukan desain 1 x 2 optical power divider baik dengan memanfaatkan pandu gelombang linier paralel maupun kombinasi pandu gelombang linier paralel dengan struktur S-bend. Terdapat dua konfigurasi pandu gelombang linier paralel yang didesain, yaitu dua pandu gelombang (directional coupler) dan tiga pandu gelombang (three-guide coupler); keduanya memanfaatkan fenomena coupled mode. Optimasi desain dilakukan dengan metode Finite Difference Beam Propagation Method (FD-BPM). Parameter yang dioptimasi adalah lebar dan tebal pandu gelombang, coupling gap, coupling length dan lebar struktur S-bend. Desain ini dioptimasi untuk beroperasi pada panjang gelombang telekomunikasi, yaitu 1,55 μm.Dari hasil optimasi ditunjukkan bahwa lebar dan tebal terbaik untuk memperoleh propagasi single mode masing-masing adalah sebesar 5 μm. Selanjutnya berdasarkan hasil optimasi lebar dan tebal pandu gelombang, ditentukan desain 1 x 2 optical power divider dengan konfigurasi dua dan tiga pandu gelombang linier paralel. Untuk konfigurasi dengan dua pandu gelombang linier paralel didapatkan hasil terbaik dengan coupling gap 7 μm dan coupling length 700 μm; sedangkan dengan konfigurasi tiga pandu gelombang linier paralel didapatkan hasil terbaik dengan coupling gap 7 μm dan coupling length 1000 μm.Dari hasil optimasi 1 x 2 optical power divider berbasis pandu gelombang linier, dilakukan optimasi desain berbasis kombinasi pandu gelombang linier paralel dan struktur S-bend. Dari hasil optimasi dan perbandingan diperoleh bahwa desain 1 x 2 optical power divider berbasis kombinasi pandu gelombang linier dan S-bend yang terbaik adalah dengan konfigurasi tiga pandu gelombang linier paralel dengan coupling gap 7 μm, coupling length 1000 μm; ukuran lebar dan tebal S-bend berturut-turut sebesar 5 μm dan lebar 6 μm. 1 x 2 optical power divider hasil desain ini mampu beroperasi menghasilkan daya keluaran relatif sebesar 93,192 % dengan coupling ratio mendekati ideal 50:50, excess loss 0,3062 dB dan power imbalance mendekati 0 dB.

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ABSTRACT

Technological advancements have encouraged the development of semiconductor materials. In the past few decades, Gallium Nitride material has attracted many researchers due to its advantages, such as high-temperature stability, high epitaxial growth rates, low power consumption, and high direct bandgap.

Until now, studies related to the use of GaN material as active photonic devices have been carried out, such as LEDs, laser diodes and detectors. However, research on GaN material on passive photonic devices, namely waveguide-based devices, has been very little.

This condition motivated us to design 1 x 2 optical power divider using both parallel linear waveguides and parallel linear waveguide combinations with the S-bend structure. Two parallel linear waveguide configurations were designed, namely two waveguides (directional coupler) and three waveguides (three-guide coupler); both of them make use of the coupled mode phenomena. Design optimization was conducted using the Finite Difference Beam Propagation Method (FD-BPM) method. The waveguide parameters optimized were width and thickness, coupling gap, coupling length and width of the S-bend structure. This design was optimized to operate at telecommunications wavelengths, 1.55 μm.

The results showed that the best width and thickness for each single-mode propagation were 5 μm. Furthermore, based on the results of the optimization of the width and thickness of the waveguide, the design of 1 x 2 optical power divider was optimized with two and three parallel linear waveguide configurations. For a configuration with two linear waveguides, the best results were achieved with coupling gap 7 μm and coupling length 700 μm; whereas with the configuration of three parallel linear waveguides, the best results obtained with a coupling gap 7 μm and coupling length 1000 μm.

Next based on the optimization 1 x 2 optical power divider using linear waveguides, design optimization was conducted for a combination of parallel linear waveguides and S-bend structures. The results showed that the best design of 1 x 2 optical power divider was achieved by using three parallel linear waveguides and S-bend structures with coupling gap 7 μm, coupling length 1000 μm; the width and thickness of S-bend were 5 μm and 6 µm wide respectively. The proposed design gave the relative output power of 93.192% with an almost ideal coupling ratio 50:50; excess loss of 0.3062 dB and power imbalance close to 0 dB.

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"ABSTRACT

The combination of the coupled mode and normal mode theories has been used to formulaic the theoretical performance represented by the coupling length and crosstalk parameters of the X-cut APE-LN SDC fabricated using the benzoic acid as the proton source, where in this case the matrix effective refractive index (MERI) method is applied for solving the symmetric and antisymmetric propagation constants of the normal modes propagating in this device. The corresponding near field method has been used to experimentally determine its crosstalk.

The actual performance of this device is characterized by comparing the theoretically calculated with the experimentally determined crosstalk parameters. A software computer program has been developed in order to numerically characterize the entire characteristic and performance of the SDC under study.

For the SDC under study, the best crosstalk obtained at the operating wavelength lamda =1.3 micrometer is ~0.21 dB for the interaction length L = 6 mm and the gap separation g = 5 mm. Its coupling length is ~ 1.33 mm. The propagation constant of the corresponding individual single-mode X-cut APE-LN channel waveguide making up this SDC is beta = 10.37901 micrometer, and thereby its effective refractive index is N cπ= 2.14743330.

It has been shown that the fabricated SDC is very lossy. It has been deduced that its bad performance predominantly caused by the side diffusion effect, corresponding to the fabrication problem, where in this case the substrate sample has been not coated first with the buffer layer when the deposition of substrate sample with the aluminum mask was to be performed in the fabrication stages.

Moreover, in this case only the simple annealing has been performed. The successive annealing process in order to reduce the coupling loss has been not applied yet. Under the assumption that the fabrication tolerances are such that the practical devices with coupling loss below 0.25 dB are feasible, the fabricated SDC under study is a 3 dB coupler. "